ProTaper – ProTaper Rear Sprockets - Steel, including CS4 steel rear sprockets in 37 and 38 tooth sizes for 08-14 Kawasaki KFX450 and 08-12 KTM 450-525 machines, is the durability answer for riders who wear out aluminum too quickly. Where a lightweight sprocket is chosen for low rotating mass, a CS4 steel rear sprocket is chosen for service life, and that trade makes sense on heavier quads, desert bikes and machines that spend their days in sand, gravel and grit. Steel teeth resist the abrasive blasting thrown up by a spinning rear tire, so tooth flanks stay square far longer and the chain keeps riding on full-depth valleys instead of hooked, undercut stubs that stretch a chain prematurely. Coverage here is focused: 08-14 Kawasaki KFX450 and 08-12 KTM 450-525 applications in 37 and 38 teeth, giving a choice between slightly taller gearing for top speed and a shorter setup for stronger acceleration. Because worn gearing accelerates wear on everything else in the driveline, a sprocket that holds its shape protects your chain and countershaft too. Running a ProTaper steel sprocket means consistent drive over long, punishing seasons.